Commit Graph

2 Commits

Author SHA1 Message Date
6550cd3970 Remove overhead: diagnostic + counters for fast path
### Changes:
1. **Removed diagnostic from wrapper** (hakmem_tiny.c:1542)
   - Was: getenv() + fprintf() on every wrapper call
   - Now: Direct return tiny_alloc_fast(size)
   - Relies on LTO (-flto) for inlining

2. **Removed counter overhead from malloc()** (hakmem.c:1242)
   - Was: 4 TLS counter increments per malloc
     - g_malloc_total_calls++
     - g_malloc_tiny_size_match++
     - g_malloc_fast_path_tried++
     - g_malloc_fast_path_null++ (on miss)
   - Now: Zero counter overhead

### Performance Results:
```
Before (with overhead):  1.51M ops/s
After (zero overhead):   1.59M ops/s  (+5% 🎉)
Baseline (old impl):     1.68M ops/s  (-5% gap remains)
System malloc:           8.08M ops/s  (reference)
```

### Analysis:
**What was heavy:**
- Counter increments: ~4 TLS writes per malloc (cache pollution)
- Diagnostic: getenv() + fprintf() check (even if disabled)
- These added ~80K ops/s overhead

**Remaining gap (-5% vs baseline):**
Box Theory (1.59M) vs Old implementation (1.68M)
- Likely due to: ownership check in free path
- Or: refill backend (sll_refill_small_from_ss vs hak_tiny_alloc x16)

### Bottleneck Update:
From profiling data (2,418 cycles per fast path):
```
Fast path time: 49.5M cycles (49.1% of total)
Refill time:    51.3M cycles (50.9% of total)

Counter overhead removed: ~5% improvement
LTO should inline wrapper: Further gains expected
```

### Status:
 IMPROVEMENT - Removed overhead, 5% faster
 STILL SHORT - 5% slower than baseline (1.68M target)

### Next Steps:
A. Investigate ownership check overhead in free path
B. Compare refill backend efficiency
C. Consider reverting to old implementation if gap persists

Related: LARSON_PERFORMANCE_ANALYSIS_2025_11_05.md
2025-11-05 06:25:29 +00:00
52386401b3 Debug Counters Implementation - Clean History
Major Features:
- Debug counter infrastructure for Refill Stage tracking
- Free Pipeline counters (ss_local, ss_remote, tls_sll)
- Diagnostic counters for early return analysis
- Unified larson.sh benchmark runner with profiles
- Phase 6-3 regression analysis documentation

Bug Fixes:
- Fix SuperSlab disabled by default (HAKMEM_TINY_USE_SUPERSLAB)
- Fix profile variable naming consistency
- Add .gitignore patterns for large files

Performance:
- Phase 6-3: 4.79 M ops/s (has OOM risk)
- With SuperSlab: 3.13 M ops/s (+19% improvement)

This is a clean repository without large log files.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
2025-11-05 12:31:14 +09:00